The prior art includes a number of examples of child carrying devices usable both as backpacks and strollers. For example, U.S. Pat. No. 3,984,115 discloses a convertible baby carrier that can function as a backpack or as an upright stroller. In this device, the forward and rear wheels separately pivot from retracted to extended positions. U.S. Pat. No. 4,157,837 discloses a device that can function as a backpack, a baby seat, a two-wheeled stroller, and a recliner or baby bed. The stroller handle pivots downward to form part of the support in the baby seat mode. The prior art also includes a large number of examples of strollers that may be collapsed for transportation or storage.
In the design of a device that can function both as a backpack and as a stroller, there is a trade-off between the structural rigidity and stability of the device when it is used as a stroller, and the weight of the device when it is used as a backpack. Prior designs, including those mentioned above, have tended towards the production of lightweight devices that have little structural rigidity. Prior collapsible strollers, on the other hand, have tended to be comparatively massive structures that would be ill-suited for use as backpacks.